Antarctica is the most pristine place on Earth, having only been visited by humans in the last 200 years, and being tens of thousands of miles from the nearest land. But these days, around 40,000 tourists and hundreds of scientists visit the Antarctic every year, and with them come stowaways in the form of bugs, beetles and plants. As a result, the ice -free areas of the Antarctic are at severe risk of invasion. Is it too late to do anything about it?

Longitude Prize: Water

How can we ensure everyone can have access to safe and clean water? Water is becoming an increasingly scarce resource. 44 per cent of the world's population and 28 per cent of the world's agriculture are in regions where water is scarce. The challenge is to alleviate the growing pressure on the planet's fresh water by creating a cheap, environmentally sustainable desalination technology. London's Becton desalination plant is expensive to run, and so used for emergencies only. Marnie Chesterton meets some Danish chemists using membranes from nature which could help make salt water drinkable, without the energy requirement of current technology.

Patents in science

European Inventor Award winner Christofer Toumazou explains his invention - a USB microchip that reads a patient's DNA. He tells Adam Rutherford how the patent system has protected his ideas.

Longitude Prize: Antibiotics

Dame Sally Davies explains why, in an era of growing antibiotic resistance, it's important to have a cheap, easy-to-use test to identify bacteria. Muna Anjum from the Animal Health and Veterinary Laboratories Agency is working on identifying those resistance genes in certain bacteria. Paul Freemont's team at Imperial College is using synthetic biology to build a device that can detect specific bacteria - precisely the sort of work that might answer the Longitude Prize's challenge.

Producer: Fiona Roberts.